/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.resolver;

import static io.netty.util.internal.ObjectUtil.checkNotNull;

import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.Promise;
import io.netty.util.internal.TypeParameterMatcher;
import io.netty.util.internal.UnstableApi;
import java.net.SocketAddress;
import java.nio.channels.UnsupportedAddressTypeException;
import java.util.Collections;
import java.util.List;

/**
 * A skeletal {@link AddressResolver} implementation.
 */
@UnstableApi
public abstract class AbstractAddressResolver<T extends SocketAddress> implements
    AddressResolver<T> {

  private final EventExecutor executor;
  private final TypeParameterMatcher matcher;

  /**
   * @param executor the {@link EventExecutor} which is used to notify the listeners of the {@link
   * Future} returned by {@link #resolve(SocketAddress)}
   */
  protected AbstractAddressResolver(EventExecutor executor) {
    this.executor = checkNotNull(executor, "executor");
    matcher = TypeParameterMatcher.find(this, AbstractAddressResolver.class, "T");
  }

  /**
   * @param executor the {@link EventExecutor} which is used to notify the listeners of the {@link
   * Future} returned by {@link #resolve(SocketAddress)}
   * @param addressType the type of the {@link SocketAddress} supported by this resolver
   */
  protected AbstractAddressResolver(EventExecutor executor, Class<? extends T> addressType) {
    this.executor = checkNotNull(executor, "executor");
    matcher = TypeParameterMatcher.get(addressType);
  }

  /**
   * Returns the {@link EventExecutor} which is used to notify the listeners of the {@link Future}
   * returned by {@link #resolve(SocketAddress)}.
   */
  protected EventExecutor executor() {
    return executor;
  }

  @Override
  public boolean isSupported(SocketAddress address) {
    return matcher.match(address);
  }

  @Override
  public final boolean isResolved(SocketAddress address) {
    if (!isSupported(address)) {
      throw new UnsupportedAddressTypeException();
    }

    @SuppressWarnings("unchecked") final T castAddress = (T) address;
    return doIsResolved(castAddress);
  }

  /**
   * Invoked by {@link #isResolved(SocketAddress)} to check if the specified {@code address} has
   * been resolved already.
   */
  protected abstract boolean doIsResolved(T address);

  @Override
  public final Future<T> resolve(SocketAddress address) {
    if (!isSupported(checkNotNull(address, "address"))) {
      // Address type not supported by the resolver
      return executor().newFailedFuture(new UnsupportedAddressTypeException());
    }

    if (isResolved(address)) {
      // Resolved already; no need to perform a lookup
      @SuppressWarnings("unchecked") final T cast = (T) address;
      return executor.newSucceededFuture(cast);
    }

    try {
      @SuppressWarnings("unchecked") final T cast = (T) address;
      final Promise<T> promise = executor().newPromise();
      doResolve(cast, promise);
      return promise;
    } catch (Exception e) {
      return executor().newFailedFuture(e);
    }
  }

  @Override
  public final Future<T> resolve(SocketAddress address, Promise<T> promise) {
    checkNotNull(address, "address");
    checkNotNull(promise, "promise");

    if (!isSupported(address)) {
      // Address type not supported by the resolver
      return promise.setFailure(new UnsupportedAddressTypeException());
    }

    if (isResolved(address)) {
      // Resolved already; no need to perform a lookup
      @SuppressWarnings("unchecked") final T cast = (T) address;
      return promise.setSuccess(cast);
    }

    try {
      @SuppressWarnings("unchecked") final T cast = (T) address;
      doResolve(cast, promise);
      return promise;
    } catch (Exception e) {
      return promise.setFailure(e);
    }
  }

  @Override
  public final Future<List<T>> resolveAll(SocketAddress address) {
    if (!isSupported(checkNotNull(address, "address"))) {
      // Address type not supported by the resolver
      return executor().newFailedFuture(new UnsupportedAddressTypeException());
    }

    if (isResolved(address)) {
      // Resolved already; no need to perform a lookup
      @SuppressWarnings("unchecked") final T cast = (T) address;
      return executor.newSucceededFuture(Collections.singletonList(cast));
    }

    try {
      @SuppressWarnings("unchecked") final T cast = (T) address;
      final Promise<List<T>> promise = executor().newPromise();
      doResolveAll(cast, promise);
      return promise;
    } catch (Exception e) {
      return executor().newFailedFuture(e);
    }
  }

  @Override
  public final Future<List<T>> resolveAll(SocketAddress address, Promise<List<T>> promise) {
    checkNotNull(address, "address");
    checkNotNull(promise, "promise");

    if (!isSupported(address)) {
      // Address type not supported by the resolver
      return promise.setFailure(new UnsupportedAddressTypeException());
    }

    if (isResolved(address)) {
      // Resolved already; no need to perform a lookup
      @SuppressWarnings("unchecked") final T cast = (T) address;
      return promise.setSuccess(Collections.singletonList(cast));
    }

    try {
      @SuppressWarnings("unchecked") final T cast = (T) address;
      doResolveAll(cast, promise);
      return promise;
    } catch (Exception e) {
      return promise.setFailure(e);
    }
  }

  /**
   * Invoked by {@link #resolve(SocketAddress)} to perform the actual name resolution.
   */
  protected abstract void doResolve(T unresolvedAddress, Promise<T> promise) throws Exception;

  /**
   * Invoked by {@link #resolveAll(SocketAddress)} to perform the actual name resolution.
   */
  protected abstract void doResolveAll(T unresolvedAddress, Promise<List<T>> promise)
      throws Exception;

  @Override
  public void close() {
  }
}
